I thought I would share my first build for interest, and provide some of the lessons I learned.

RCTimer Spider Frame

Universal GPS folding mount

4x RC Tiger 30A ESCs

4x RC Tiger MT4006-13 740Kv

4x APC 10x47 Props

3DR PPM Encoder

Turnigy 5000mAh 4s1P Lipo

Hobby King PDB

FlySky FS-TH9X 2.4GHz 9ch Transmitter

FlySky FS-R9B Receiver

Arduflyer/APM Power Module XT60 Kit

Raspberry Pi 2 Model B

Navio+

3D Printed Navio Casing

GPS/GNSS antenna MCX

Some lessons learned along the way:

If possible, find a battery (and charger) which has the same connector as the power module you are using. If not possible, you will need to solder the connectors on yourself as I did.

Rather use a PCB for power distribution than trying to solder wires of the ESCs together and making a mess. Its much neater.

Calibrating all the sensors on the autopilot is much easier if you can afford telemetry with your build. In my case, I had to use an Ethernet cable hooked up to my wifi modem at home. The cable gets in the way when you are, for example, calibrating the compass.

Some proficiency with using the terminal is great for trouble shooting communication problems between the GCS and the raspberry if your GCS is installed on a Linux based OS.

Make use of the Forum!

What lessons have you experienced during your first build that might serve good advice to newbies planning their first build??

Calibrating all the sensors on the autopilot is much easier if you can afford telemetry with your build. In my case, I had to use an Ethernet cable hooked up to my wifi modem at home. The cable gets in the way when you are, for example, calibrating the compass.

We use usb wi-fi dongles for that. Very handy when doing calibrations and even for flying in short range.
You can find a list of Wi-Fi dongles compatible with Raspberry Pi here.